Introduction

The Canon EF 17-40mm f/4 USM L has already been tested on the old EOS 350D @ 8mp so this is only a retest based on the EOS [email protected] 15mp (APS-C). Therefore you may forgive us that we simply reused portions of the old article.

The Canon EF 17-40mm f/4 USM L is one of the most popular L class lenses thanks to its relatively affordable price and its dual purpose scope - it can serve as a "27-64mm" standard zoom lens on APS-C DSLRs and it's an ultra-wide zoom lens with an attractive range on full format DSLRs.

The build quality of this lens is exceptionally high just as you would expect it from a Canon L lens. No wobbling whatsoever and smooth controls - almost perfect. The lens is also designed to survive in harsh conditions with a sealing against dust and moisture. The outer length of the lens remains constant although the inner lens tube moves a little according to the zoom setting. Needless to say - the front element does not rotate during focusing or zooming operations.

The lens has a ring-type USM drive based on a front-focusing system resulting in an extremely fast AF speed. AF accuracy was also not an issue during the field tests. Typical for ring-type USM lenses full-time manual focusing is always possible in one-shot AF mode.